An electric solder iron is an indispensable tool in electric parts soldering. When using an electric iron, a solder wire is melted to join electric parts. Therefore, generally, when working, a user must hold the electric solder iron with one hand and grasp the solder wire with the other. As a consequence, the parts being soldered cannot be suitably retained by the user, and thus a great inconvenience is caused. Therefore applicant has developed an auxiliary soldering device for electric solder iron, which enables a user to simultaneously hold the electric solder iron and the solder wire with a single hand, wherein the solder wire is controllably and easily pushed forward for soldering.